A widely used and successful commercial process for synthesizing acetic acid involves the catalyzed carbonylation of methanol with carbon monoxide. The catalyst contains rhodium and/or iridium and a halogen promoter, typically methyl iodide. The reaction is conducted by continuously bubbling carbon monoxide through a liquid reaction medium in which the catalyst is dissolved. The reaction medium comprises acetic acid, methyl acetate, water, methyl iodide and the catalyst. Conventional commercial processes for carbonylation of methanol include those described in U.S. Pat. Nos. 3,769,329, 5,001,259, 5,026,908, and 5,144,068, the entire contents and disclosures of which are hereby incorporated by reference. Another conventional methanol carbonylation process includes the Cativa™ process, that is discussed in Jones, J. H. (2002), “The Cativa™ Process for the Manufacture of Acetic Acid,” Platinum Metals Review, 44(3): 94-105, the entire content and disclosure of which is hereby incorporated by reference.
The crude acetic acid product from the reactor is processed in a purification section to remove impurities and recover acetic acid. These impurities, that may be present in trace amount, affect the quality of acetic acid, especially as the impurities are circulated through the reaction process, which, among other things, can result in the build up over time of these impurities. Conventional purification techniques to remove these impurities include treating the acetic acid product streams with oxidizers, ozone, water, methanol, activated-carbon, amines, and the like. The treatments may also be combined with the distillation of the crude acetic acid product. Generally, in many chemical processes such as acetic acid production, distillation columns consume a significant amount of energy. The distillation columns may each independently receive the energy necessary to drive the separation within the column. The present invention provides new and improved processes to advantageously increase the overall efficiency of an acetic acid production process by providing the energy required to drive separation in a separation system, preferably a light ends column, from another location within the system.